How to Generate a UUID in JavaScript, Java, and Python

Last updated: October 9, 2026

A UUID (Universally Unique Identifier) is a 128-bit identifier defined by RFC 9562. It is usually written as 36 characters in 8-4-4-4-12 form, such as 3f2c9e5a-7b4d-4e2a-9c1f-8d3b6a2e4f51. UUIDs let independent systems create unique IDs without a central coordinator, which is why they show up everywhere from database primary keys to request tracing.

Generating a UUID in JavaScript

Modern browsers and Node.js ship crypto.randomUUID(), which returns a UUID v4. No library is required. It works in browsers in secure contexts (HTTPS or localhost) and in Node.js 14.17 and later.

// JavaScript (browsers, Node.js 14.17+)
const id = crypto.randomUUID();
console.log(id); // e.g. "3f2c9e5a-7b4d-4e2a-9c1f-8d3b6a2e4f51"

Generating a UUID in Java

java.util.UUID.randomUUID() generates a UUID v4 out of the box. For UUID v7 (time-ordered, recommended for database keys), use the popular uuid-creator library, since the JDK does not yet ship a built-in v7 generator.

// Java
import java.util.UUID;

UUID id = UUID.randomUUID(); // UUID v4

// UUID v7 with the uuid-creator library (com.github.f4b6a3:uuid-creator)
import com.github.f4b6a3.uuid.UuidCreator;
UUID ordered = UuidCreator.getTimeOrderedEpoch();

Generating a UUID in Python

The standard library has covered UUID v4 for years. Python 3.14 added built-in support for UUID v7 (uuid.uuid7()), matching the time-ordered format from RFC 9562.

# Python
import uuid

print(uuid.uuid4())  # UUID v4
print(uuid.uuid7())  # UUID v7 (Python 3.14+)

UUID v4 vs UUID v7

The trade-off: v7 values reveal when they were created, so do not use them where IDs must be unguessable. Our UUID v4 vs v7 guide goes deeper with more code examples.